The Mezzanine Hall on the second floor of the Mercado Building was originally an auditorium complete with a stage, dressing rooms, electric lights, and seating capacity for several hundred. During this time, it was also used for local theater productions and parties. In 1885, a new floor was installed to permit roller skating.

In 1916, the Laredo Women's Club used a portion for a small library and in the early 1930's its present floor was install and the Mezzanine Hall became Laredo's first Public Library. The Library was moved to Bruni Plaza in 1975.

The Mezzanine Hall is approximately 2,850 sqft high ceilings and large windows covering the west and east walls. with with